The invention relates to double-walled prefabricated metal chimneys, and more particularly to a slidable joint for such chimneys.
Double-walled prefabricated metal chimneys have previously been used, with some variation in form, as an easily assembled and installed means of conveying smoke and flue gases to the outside of a dwelling or other building. The central space defined by the inner chimney wall carries the smoke and gases, while the annular space between the inner and outer walls provides an insulating space so that the outer wall remains relatively cool, and the chimney may be placed inside the building walls without creating a fire hazard. Sometimes the annular space in the chimney is open to the atmosphere at its upper and lower ends, or to an air circulating system, so that further heat can be exhausted or conducted into a space to be heated.
A prefabricated double-walled metal chimney assembly is illustrated and described in my U.S. Pat. No. 3,902,744.
Previous double-walled chimney assemblies have employed several types of expansion joint for thermal expansion and contraction, including a bellows-type joint in the inner chimney wall. However, none has provided an efficient combination joint for handling such expansion and contraction as well as for facilitating length adjustment during installation, as does the present invention described below.